Einstein, Podolsky and Rosen (epr) illustrated their celebrated 1935 argument against the completeness of quantum mechanics with a Gedankenexperiment [9]. They considered a 1-dimensional two-particle system in a peculiar improper quantum-mechanical state such that either the momentum or the position of one particle is predictable (i.e. probability equal to 1) as soon as the position or the momentum of the other particle is measured.